Electronic and/or integrated circuit (“IC”) devices, e.g., microprocessors, memory devices, and the like, are becoming smaller while heat dissipation requirements are increasing. In order to dissipate the heat generated by these devices, heat spreaders and/or heat sinks are used.
Several materials and designs have been disclosed for the management and removal of heat from electronic devices. U.S. Pat. No. 5,296,310 discloses a hybrid structural device of a high thermal conductivity material sandwiched between a pair of face sheets comprising a metal or matrix-reinforced metal. The core material can be a highly ordered pyrolytic graphite, compression annealed pyrolytic graphite (CAPG), synthetic diamond, composites using these materials, or the like U.S. Pat. No. 6,215,661 discloses a heat spreader comprising an L-shaped plate of thermal pyrolytic graphite encapsulated in aluminum. U.S. Pat. No. 5,958,572 discloses a heat spreading substrate comprising an insert of thermal pyrolytic graphite (“TPG”), a diamond-like-carbon, and the like material having a plurality of vias formed within, to optimize heat flow transfer through the plurality of vias.
Some forms of pyrolytic graphite in the prior art, particularly those made by chemical vapor deposition processes, suffer from non-uniform thickness, which is due to variations in crystallographic plane thickness. Adjacent crystallographic layers are substantially parallel, but variations on the crystallographic scale accumulate over macroscopic thicknesses. For example, at 1 mm, the natural layer plane surfaces are not parallel. Thermal pyrolytic graphite “tiles” having the requisite thermal conductivity properties are available in the art for the making of heat spreader. However, they have relatively small dimensions, e.g., 2 cm width and 0.1 cm thick, for making relatively small heat spreaders. U.S. Pat. No. 6,407,902 offers a solution around the small-sized pyrolytic graphite tiles with heat spreaders comprising thermal pyrolytic graphite flakes incorporated in a matrix material. The composite graphite material can be machined into spreaders of desired dimensions, obviating the use of multiple fixed small-sized graphite tiles in the art.
There exists a need for a high thermal conductivity material of improved quality and size for use in devices for removing heat from electronic and IC equipment, i.e., a material suitable as a feedstock for making heat spreaders, heat inks, and the like. There is also the need for a process to make such high thermal conductivity feedstock.